Boiler losing pressure? What to check and when to call us
Boiler losing pressure? What to check and when to call us
Advice · Boiler problems
Low boiler pressure is one of the most common reasons boilers stop working. Here’s what it means, what you can safely check yourself, and when to call a Gas Safe engineer.
What should the pressure be?
Most sealed central heating systems should sit at around 1 to 1.5 bar when the heating is off and cold, rising a little when the system is hot. Check your boiler manual for the exact figure. If the gauge drops below about 1 bar, many boilers show a fault code or stop working.
How to top up the pressure
Most boilers have a filling loop: a silver flexible hose with one or two taps, or a built-in key or lever under the boiler. With the heating off and cool, open the valve slowly while you watch the gauge, close it when you reach the right pressure, then reset the boiler. Your boiler manual will show the exact method for your model. If you’re not comfortable doing it, call us.
Why does a boiler keep losing pressure?
Topping up once in a while is normal, especially after bleeding radiators. If you’re topping up every few days or weeks, there’s usually an underlying cause:
- A small leak from a radiator valve, pipe joint or the boiler itself
- A faulty pressure relief valve letting water out through the pipe outside
- A failed expansion vessel inside the boiler
- Water released when radiators were bled
When to call a Gas Safe engineer
- The pressure keeps dropping after you top it up
- You can see water dripping from the boiler or the small copper pipe outside
- The pressure goes very high (around 3 bar) when the heating is on
- The boiler shows a fault code that won’t clear
Never remove the boiler casing yourself. Only a Gas Safe registered engineer should work inside a gas boiler. Our boiler repair engineers can find and fix the cause, and fix leaks on your central heating.
Frequently asked questions
Is low boiler pressure dangerous?
Low pressure itself isn’t dangerous. The boiler simply switches off to protect itself. But a persistent leak can damage your home and should be fixed.
Can a service stop pressure problems?
An annual service includes checking the expansion vessel and pressure, which helps catch problems early.
More advice
Should I repair or replace my boiler?
An honest way to decide, from engineers who do both.
Read the guide →How much does a boiler service cost in Leeds?
What’s included, how often you need one and what it costs.
Read the guide →How much does a new boiler cost in Leeds?
Typical prices, what affects them and what’s included.
Read the guide →Boiler still losing pressure?
Call 0113 532 7670 and we’ll get it sorted.
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